This invention has to do with internal combustible fuel burning reciprocating engines. There are several applicable types of U.S. patent classifications for this application, such as internal combustion engines where mechanical power is needed for various uses.
All internal combustion engines to date are very inefficient where a big portion of the heat energy is wasted and not effectively doing all the work that it could be doing (100% input with 20-30% output).
The wasted heat energy has to be carried away by a radiator or other means of cooling, the heat and pressure in a combustion chamber is the highest when the crank and piston's position is at top dead center. That is when the engine's piston and crank can do no work, driving the heat into the head and piston. The energy has no place to go.
As the crank moves down and starts to gain a mechanical advantage the pressure in that cylinder continuously drops off.
We have been making engines this way for about 150 years, and for most engines there is only one power stroke every forth cycle, every two revolutions of the crank, and very little change has been made in the design since the beginning of the internal combustion engine. We have used this same engine design for a long time.